System for 3D printing

ABSTRACT

An additive manufacturing (AM) system includes a carriage that deposits material in a defined pattern and a building platform that receives material deposited from the carriage. The carriage includes a pre-heating assembly with a plurality of pre-heating chambers and a printing block with a plurality of slots for receiving a plurality of printing heads. The carriage is equipped with more pre-heating chambers than head slots.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/746,808 filed on Jan. 23, 2018, which is a National Phase of PCTPatent Application No. PCT/IL2016/050837 having International FilingDate of Aug. 1, 2016, which claims the benefit of priority under 35 USC§ 119(e) of U.S. Provisional Patent Application No. 62/200,061 filed onAug. 2, 2015. The contents of the above applications are allincorporated by reference as if fully set forth herein in theirentirety.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to freeformmanufacturing and, more particularly, but not exclusively, to a threedimensional (3D) printing.

Additive manufacturing (AM) is generally a process in which a 3D objectis manufactured utilizing a computer model of the object. Such a processis used in various fields, such as design related fields for purposes ofvisualization, demonstration and mechanical prototyping, as well as forrapid manufacturing.

The basic operation of any AM system consists of slicing a 3D computermodel into thin cross sections, translating the result intotwo-dimensional position data and feeding the data to a controller of asystem that constructs a 3D structure in a layer-wise manner.

AM entails many different approaches to the method of fabrication,including 3D inkjet printing, laminated object manufacturing, fuseddeposition modeling and others.

In 3D printing processes, for example, a building material is dispensedfrom a carriage including one or more printing heads. Each of theprinting heads has a set of nozzles from which material can beselectively dispensed on a supporting structure to form one layer at atime. Depending on the building material, the layers may then be curedor solidified using a suitable device that is also carried on thecarriage. The building material may include modeling material, whichforms the object, and support material, which supports the object as itis being built. The carriage scans the supporting structure and patternsit. Various 3D printing techniques are disclosed in, e.g., U.S. Pat.Nos. 6,259,962, 6,569,373, 6,658,314, 6,850,334, 7,183,335 7,209,797,7,225,045, 7,300,619, 7,364,686, 7,500,846, 7,658,976, 7,962,237,8,781,615 and 9,031,680, and U.S. Application Publication Nos.20130040091 and 20150035186, all of the same Assignee, the contents ofwhich are hereby incorporated by reference.

For example, U.S. Pat. No. 8,781,615 entitled “Rapid ProductionApparatus with Production Orientation Determination” discloses a methodof producing an object by sequentially printing layers of constructionmaterial one on top of the other.

The method includes providing the construction material at a first lowertemperature, flowing the construction material through a heated flowpath in a flow structure to heat the construction material anddelivering the heated construction material to a heated reservoir in aprinting head. The heated construction material is then dispensed fromthe reservoir to build the object layer by layer. In one example it isdescribed that one or more spiral shaped flow channels are used toprovide sufficient length to enable efficient heat transfer to theflowing material.

U.S. Patent Application Publication No. 20150035186 entitled “System andMethod for Depositing Liquids,” describes a printing head for a printingsystem. The printing head comprises a plurality of compartments, eachhaving an outlet port for depositing liquid and an inlet port separatelyconnectable to a separate liquid container. At least two compartmentsare in controllable fluid communication with each other, and theprinting head comprises an arrangement of sensors configured forgenerating signals indicative of (i) a filling state of eachcompartment, and (ii) a fluid communication state between the at leasttwo compartments. Optionally, at least two compartments occupy a chamberand are separated by at least a partition, and wherein said fluidcommunication is via a liquid passage in said chamber.

SUMMARY OF THE INVENTION

According to an aspect of some embodiments of the present inventionthere is provided a 3D printer that provides full color printing,printing with a broad array of mechanical properties and/or printingwith a broad range of different materials using relatively few printingheads. Optionally, each printing head simultaneously dispenses twodifferent materials during printing. According to some embodiments ofthe present invention, a carriage of the 3D printer has a compact designthat provides for significantly increasing the range of buildingmaterial without increasing or significantly increasing the size of thecarriage of the printer.

According to an aspect of some embodiments of the present inventionthere is provided an additive manufacturing (AM) system comprising: acarriage comprising: a pre-heating assembly comprising a plurality ofpre-heating chambers; and a printing block comprising a plurality ofslots for receiving a plurality of printing heads, wherein the carriageincludes more pre-heating chambers than head slots; and a buildingplatform configured to receive material deposited from the carriage.

Optionally, the printing block is formed with a pair of reservoirsconfigured to be in fluid communication with one of the plurality ofprinting heads when installed in one of the plurality of slots.

Optionally, printing block is formed with a pair of reservoirssurrounding each of the plurality of slots, wherein each pair isconfigured to be in fluid communication with one of the plurality ofprinting heads installed in the printing block.

Optionally, each of the pair is configured to be in fluid communicationwith a separate nozzle array of the one of the plurality of printingheads.

Optionally, each of the plurality of pre-heating chambers is in fluidcommunication with one of the reservoirs formed in the printing block.

Optionally, the pair is separated by a separating wall.

Optionally, the separating wall is configured to allow selected floodingbetween the pair of reservoirs.

Optionally, the plurality of printing heads is configured tosimultaneously receive material from all the plurality of pre-heatingchambers.

Optionally, the system includes heating plates installed on two oppositefacing surfaces of the printing block.

Optionally, at least one of the plurality of pre-heating chambersincludes a worm screw channel configured to direct material through theone of the plurality of pre-heating chambers.

Optionally, the worm screw is formed from a heat conductive material.

Optionally, the material is directed from a pre-heating chamber to aprinting head reservoir via a dedicated block cover channel.

Optionally, each of the plurality of pre-heating chambers includes aworm screw.

Optionally, the carriage includes a hardening unit configured to hardena layer of material dispensed on the building platform.

Optionally, the carriage includes a leveling device configured to levela layer of material dispensed on the building platform.

Optionally, the AM system is a three dimensional ink-jet printer.

Optionally, the pre-heating assembly is divided into a first sectionincluding a first pre-heating chamber and a second section including asecond plurality of pre-heating chamber, wherein the first section ispre-heated with a first heating element and wherein the second sectionis heated with a second separate heating element.

Optionally, the printing block includes a least one reservoir associatedwith each of the slots and wherein the printing block includes openingsthat are configured to thermally insulate material received in one ofthe reservoirs from material received in other reservoirs of theprinting block.

Optionally, the pre-heating assembly is divided into at least a firstsection and a second section, wherein the first section includes a firstpre-heating chamber and the second section includes a second pre-heatingchamber, and wherein the first section is pre-heated with a firstheating element and the second section is heated with a second separateheating element.

According to an aspect of some embodiments of the present invention,there is provided a method comprising: heating a plurality of differentmaterials in separate chambers; simultaneously delivering contents ofeach of the plurality of different materials to a plurality of printingheads, wherein the plurality of different materials exceeds in numberthe plurality of printing heads; and dispensing all the plurality ofdifferent materials with the printing heads by three dimensional inkjetprinting.

Optionally, each of the plurality of different materials is directed tothe printing heads via dedicated pairs of reservoirs formed in theprinting block configured to hold the printing heads, wherein each pairis in fluid communication with one of the plurality of printing heads.

Optionally, the method includes simultaneously directing material fromthe pair of reservoirs to separate nozzle arrays of the printing head.

Optionally, the method includes directing the material from the base ofa pre-heater worm screw via a dedicated block cover channel to aprinting head reservoir.

Optionally, one of the plurality of different materials is heated to afirst temperature and another of the plurality of different materials isheated to a second temperature.

Optionally, the one of the plurality of different materials is supportmaterial and the other of the plurality of different materials ismodeling material.

Optionally, the support material is heated to a temperature that is 2-10degrees lower than the modeling material.

Optionally, the support material is heated and maintained at atemperature of 65° C. and the modeling material is heated and maintainedat a temperature of 70° C.

Optionally, yet another of the plurality of different materials isheated to a third temperature.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, exemplarymethods and/or materials are described below. In case of conflict, thepatent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of embodiments of the invention. In this regard, thedescription taken with the drawings makes apparent to those skilled inthe art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 is a simplified block diagram of an AM system in accordance withsome embodiments of the invention;

FIG. 2 is a front perspective view of an exemplary carriage inaccordance with some embodiments of the present invention;

FIGS. 3A-3B are exemplary front and back perspective views showinginternal components of a pre-heater for an AM system in accordance withsome embodiments of the present invention;

FIG. 4A is a perspective view of a printing block in accordance withsome embodiments of the present invention;

FIG. 4B is a cross sectional side perspective view of the printing blockcut along a length of a printing head slot in accordance with someembodiments of the present invention;

FIGS. 5A-5B are exemplary perspective and top views of a printing blockbase of an AM system in accordance with some embodiments of the presentinvention;

FIG. 6 is an exemplary back perspective view of a carriage for an AMsystem in accordance with some embodiments of the present invention;

FIG. 7 is an exemplary electronic pack for an AM system in accordancewith some embodiments of the present invention;

FIG. 8 is an exemplary printing head in accordance with embodiments ofthe present invention;

FIG. 9 is an exemplary perspective view of a printing block assemblyinstalled with printing heads in accordance with some embodiments of thepresent invention;

FIG. 10 is an exemplary top view of another printing block base of an AMsystem in accordance with some embodiments of the present invention;

FIG. 11 is an exemplary perspective view of a printing block baseinstalled with two heating plates in accordance with some embodiments ofthe present invention;

FIG. 12A is a back perspective view showing the components of a printingblock assembly in surface contact with a pre-heater assembly for an AMsystem in accordance with some embodiments of the present invention;

FIG. 12B is a back perspective view showing internal components of apre-heater for an AM system that is separated into two sections inaccordance with some embodiments of the present invention;

FIG. 13 is a front perspective view of another exemplary carriage inaccordance with some embodiments of the present invention;

FIG. 14 is a perspective view showing internal components of anotherpre-heater for an AM system that is separated into two sections inaccordance with some embodiments of the present invention;

FIG. 15 is a front perspective view of yet another exemplary carriage inaccordance with some embodiments of the present invention;

FIG. 16 is a perspective view showing internal components of yet anotherpre-heater for an AM system that is separated into two sections inaccordance with some embodiments of the present invention; and

FIG. 17 is a graph showing the temperature behavior over time in variouslocations of a printing block in accordance with some embodiments of thepresent invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to freeformmanufacturing and, more particularly, but not exclusively, to a threedimensional (3D) printing.

According to some embodiments of the present invention, an AM systemprovides for simultaneously feeding building material from two differentsources to a single printing head and for simultaneously printingmaterial from the two different sources with the single printing head.In some exemplary embodiments, up to eight different materials aresimultaneously delivered to four printing heads installed in a carriageof the AM system. Optionally, three of the printing heads are operatedto print with six different colored resins and a forth printing head isoperated to print support material.

Prior to delivering the materials to the printing heads, each of thebuilding materials is pre-heated in a separate pre-heat chamber that iscarried on the carriage of the AM system. Each of the pre-heat chambersis required to provide sufficient length to enable efficient heattransfer to the flowing material. Typically, it is desirable to have acompact construction for the carriage and therefore the number ofseparate pre-heat chambers that can be included in the carriage may belimited. The present inventors have found the volume of each of thepre-heat chambers required to pre-heat the building material may bereduced by channeling the building material around a worm screw-shapedrunner. In some exemplary embodiments, a worm screw runner with adiameter that substantially matches a diameter of the pre-heat chamberis installed in each of the pre-heat chambers. The liquid buildingmaterial runs downwards around the worm screw. By reducing the volumerequired for each pre-heat chamber, more pre-heat chambers can be addedto a same size carriage and thereby compactness of the AM system isimproved. In some exemplary embodiments, the pre-heat system includestwo or more thermally independent sections that provide forsimultaneously pre-heating each section to a different temperature.Optionally, the pre-heat system provides for heating the supportmaterial chambers to a first temperature and heating the modelingmaterial to a different temperature, e.g. higher temperature.Optionally, the pre-heat system may heat each of the chambers to adifferent pre-defined temperature.

The printing heads are typically installed in a printing block that iscarried on the carriage. According to some embodiments of the presentinvention, the printing block is formed of a slot for each printing headas well as a pair of reservoirs surrounding each of the slots. Accordingto some embodiments of the present invention, outflow from each of thepre-heat chambers is directed to one of the reservoirs and the materialfeed into the reservoir is directed to a printing head via one or moreoutputs formed in the reservoir. Typically, material fed into one of apair of reservoirs provides material for printing through a first arrayof nozzles of a printing head and material fed into the other one of thepair of reservoirs provides material for printing through an alternatearray of nozzles of that printing head. In some exemplary embodiments, abaffle separating the pair of reservoirs is sized to allow controlledoverflow of material between the pair of reservoirs.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not necessarily limited in itsapplication to the details of construction and the arrangement of thecomponents and/or methods set forth in the following description and/orillustrated in the drawings. The invention is capable of otherembodiments or of being practiced or carried out in various ways.

The method and system of the present embodiments manufacture 3D objectsbased on computer object data in a layer-wise manner by forming aplurality of layers in a configured pattern corresponding to the shapeof the objects. The computer object data can be in any known format,including, without limitation, a Standard Tessellation Language (STL) ora StereoLithography Contour (SLC) format, Virtual Reality ModelingLanguage (VRML), Additive Manufacturing File (AMF) format, DrawingExchange Format (DXF), Polygon File Format (PLY) or any other formatsuitable for Computer-Aided Design (CAD).

The term “object” as used herein refers to a whole object or a partthereof.

Each layer is formed by an AM apparatus that includes a carriage whichscans a two-dimensional surface in passes and patterns it. Whilescanning, the carriage visits a plurality of target locations on thetwo-dimensional layer or surface, and decides, for each target locationor a group of target locations, whether or not the target location orgroup of target locations is to be occupied by building material, andwhich type of building material is to be delivered thereto. The decisionis made according to a computer image of the surface.

In preferred embodiments of the present invention, the AM comprises 3Dprinting, more preferably 3D inkjet printing. In these embodiments abuilding material is dispensed from a dispensing head having a set ofnozzles to deposit building material in layers on a supportingstructure. The AM apparatus thus dispenses building material in targetlocations which are to be occupied and leaves other target locationsvoid. The types of building materials can be categorized into two majorcategories: modeling material and support material. The support materialserves to form a supporting matrix or construction for supporting theobject or object parts during the fabrication process and/or otherpurposes, e.g., providing hollow or porous objects. Supportconstructions or matrices may additionally include modeling materialelements, e.g. for further support strength.

The modeling material is generally a composition which is formulated foruse in AM and which is able to form a 3D object on its own, i.e.,without having to be mixed or combined with any other substance.

The final 3D object is made of the modeling material or a combination ofmodeling materials or modeling and support materials or modificationthereof (e.g., following curing). All these operations are well-known tothose skilled in the art of solid freeform fabrication.

In some exemplary embodiments of the invention an object is manufacturedby dispensing a plurality of different modeling materials, e.g.different colored resins.

The materials are optionally and preferably deposited in layers duringthe same pass of the printing heads. The materials and combination ofmaterials within the layer are selected according to the desiredproperties of the object.

Reference is now made to FIG. 1 showing a simplified block diagram of anAM system in accordance with some embodiments of the invention.Typically, AM system 100 is a 3D droplet deposition system, e.g. inkjetprinting apparatus.

Typically, AM system 100 includes carriage 150 that scans a buildingsurface or tray 660. Typically, carriage 150 carries a pre-heatingassembly 138 comprising a plurality of pre-heat chambers 130 forpre-heating the building material, a plurality of printing heads 20 forselectively depositing material on tray 660, a leveling device 220 forleveling a printed layer and one or more hardening devices 210 forhardening the printed layer. Printing heads 20 are typically secured ona printing block 120.

Carriage 150 is preferably operative to reciprocally move over tray 660,which serves as the working surface. Tray 660 is positionedhorizontally. According to the common conventions, an X-Y-Z Cartesiancoordinate system is selected such that the X-Y plane is parallel totray 660. In use in some exemplary embodiments, carriage 150 moves in ascanning direction, which is referred to herein as the X direction, andprinting heads 20 selectively dispense building material in apredetermined configuration in the course of their passage over tray660. The building material typically comprises one or more types ofsupport material and one or more types of modeling material. The passageof printing heads 20 is followed by hardening, e.g. curing of themodeling material(s) with one of hardening devices 210. In the reversepassage of the carriage 150, back to its starting point for the layerjust deposited, an additional dispensing of building material may becarried out, according to predetermined configuration and the other ofthe hardening devices 210 is operated. In the forward and/or reversepassages of carriage 150, the layer formed may be straightened byleveling device 220, which preferably follows the path of printing heads20 in their forward and/or reverse movement. Once carriage 150 returnsto its starting point along the X direction, it may move to anotherposition along an indexing direction, referred to herein as the Ydirection, and continue to build the same layer by reciprocal movementalong the X direction. Alternately, carriage 150 may move in the Ydirection between forward and reverse movements or after more than oneforward-reverse movement. The series of scans performed by thedispensing heads to complete a single layer is referred to herein as asingle scan cycle.

Once the layer is completed, tray 660 may be lowered in the Z directionto a predetermined Z level, according to the desired thickness of thelayer subsequently to be printed. The procedure is repeated to form 3Dobject 650 in a layer-wise manner. Alternatively, carriage 150 may movein the Z-direction according to the desired thickness of the layer.

A control unit 640 controls operation of the elements included incarriage 150. Control unit 640 typically includes an electronic circuitconfigured to perform the controlling operations. Control unit 640preferably communicates with a processor 600 which transmits digitaldata pertaining to fabrication instructions based on computer objectdata, e.g., a CAD configuration represented on a computer readablemedium in a form of a Standard Tessellation Language (STL) format or thelike. Typically, processor 600 includes a memory unit and/or memorycapability for storing computer object data and for storing datapertaining to fabrication instructions based on computer object data.Typically, control unit 640 controls the voltage applied to eachprinting head 20 or nozzle array 124 and the temperature of the buildingmaterial both in the pre-heat chambers 130 and printing block 120.

Once the manufacturing data is loaded to control unit 640 it can operatewithout user intervention. In some embodiments, control unit 640receives additional input from the operator, e.g., using data processor600 or using a user interface 610 communicating with unit 640.

During operation, building material is supplied to pre-heat chambers 130for pre-heating and then fed to printing heads 20 via a plurality ofreservoirs 125 included in printing block 120. In some exemplaryembodiments, a pair of reservoirs 125 surrounds each printing head 20and supplies material to its printing head, so that each printing head20 is feed by two reservoirs 125. According to some embodiments of thepresent invention, carriage 150 includes more pre-heat chambers 130 thanprinting heads and at least one of printing heads 20 simultaneouslyreceives supply from two different pre-heating chambers 130. Typically,each pre-heating chamber 130 directs material to a different reservoir125. According to some embodiments of the present invention, eachprinting head 20 includes at least two arrays of nozzles 124 and eachreservoir 125 is in fluid communication with a dedicated array ofnozzles 124. To dispense the building material, a voltage signal isapplied to the printing heads 20 to selectively deposit droplets ofmaterial via printing head nozzles 124. The dispensing rate of each head20 depends on the number of nozzles 124, the type of nozzles and theapplied voltage signal rate (frequency). In some exemplary embodiments,each of printing heads 20 (or at least one of printing heads 20)receives building material from two different pre-heat chambers andmaterial from each pre-heat chamber is dispensed by a dedicated array ofnozzles 124.

Reference is now made to FIG. 2 showing an exemplary front perspectiveview of a carriage in accordance with some embodiments of the presentinvention. Carriage 150 includes printing block 120, a pre-heatingassembly 138 including a plurality of pre-heat chambers 130 (FIG. 1 ), apair of hardening units 210 positioned on either side of block 150 inthe X direction, and a leveling device 220 (FIG. 1 ) typically connectedto and operated with a pulley system 225. Typically hardening units 210are ultra-violet (UV) modules that emit UV beams through a radiationwindow 215.

Building material introduced to carriage 150 is first received bypre-heating assembly 138 via inlets 135. Optionally, pre-heatingassembly 138 includes eight inlets 135 for receiving up to eightdifferent types of materials, e.g. modeling and support material.Material received in pre-heating assembly 138 is typically heated to adefined temperature prior to supplying the material to printing block120. Printing block 120 typically includes a plurality of printing heads20.

Reference is now made to FIGS. 3A-3B showing exemplary front and backperspective views of internal components of a pre-heater for an AMsystem in accordance with some embodiments of the present invention.According to some embodiments of the present invention, each chamber 130in assembly 138 includes a worm screw-shaped runner 131 around whichmaterial is directed through chamber 130. Optionally, assembly 138includes eight chambers 130 for simultaneously receiving up to eightdifferent materials. Typically, a diameter of worm 131 closely matches adiameter of chamber 130 so that material introduced into chamber 130follows the spiral path provided by worm 131 to reach an outlet ofchamber 130 through a pre-heat cartridge 136. The spiral path increasesa path length that the material is required to take. This increase inpath length allows longer heat exchange.

Optionally, worm 131 is formed from heat conductive material and contactbetween the material and worm 131 improves heat transfer. The presentinventors have found that worm 131 provides for significantly increasingthe path length of material while occupying a relatively smallfootprint. By reducing the footprint, more chambers 130 and thereby alarger variety of building material can be included on a same sizecarriage 150. The present inventor has found that eight pre-heatchambers fit on a carriage size that would otherwise typically hold fourpre-heat chambers when using pre-heating assembly 138. Typically,pre-heat assembly 138 heats contents of all chambers 130 to or nearjetting temperature before entering the printing head reservoirs so thatthe material can be ready for jetting also at high throughput.Optionally, pre-heating assembly 138 may selectively heat each or aportion of the chambers to a different temperature.

According to some embodiments of the present invention, pre-heatingassembly 138 includes a heating plate 132 that heats contents in eachchamber 130 of assembly 138. Optionally, heating plate 132 is a 54 Wattheater that is covered with a thermal insulator 133 on a surfaceopposite the surface facing chambers 130. Typically, assembly 138additionally includes a temperature sensor 134 for monitoring thetemperature of assembly 138. In some exemplary embodiments, a durationof heat exchange in assembly 138 is controlled by controllingtemperature of plate 132. Typically, inlets 135 are formed throughflange 137 and sealed with o-rings.

Reference is now made to FIGS. 4A-4B showing a perspective view of partsof a printing block assembly, FIG. 4A showing perspective view of aprinting block and FIG. 4B showing a cross sectional side perspectiveview cut along a length of a printing head slot in accordance with someembodiments of the present invention.

According to some embodiments of the present invention, pre-heatingassembly 138 is mounted on manifold 320 including a check valve 310 foreach chamber 130. Manifold 320 controls delivery of material to printingblock 120 and also prevents unwanted dripping while a chamber 130 is notin use. In some exemplary embodiments, printing block 120 is installedwith a plurality of vacuum inlets 315 for evaluating required inletamounts. Optionally, printing block 120 includes one vacuum inlet 315per printing head 20. Alternatively, printing block 120 includes onevacuum inlet 315 per pre-heat chamber 130.

Optionally, printing block 120 includes a block base 325, a block cover335 and a top insulator 330 all of which define a plurality of slots 25for inserting each of printing heads 20. Typically, each printing headis secured into a slot 25 with spring loaded lock screws 345, e.g.secured with a pair of spring loaded lock screws 345, one on either sideof slot 25. Typically, printing block 120 is heated to maintain materialaccumulated in printing block 120 at a desired temperature. Optionally,heating is provided with heating plate 355 installed on two oppositelyfacing block sides spaced along a Y direction. Optionally heating plate355 is a 44 Watt heater. Typically, heat level is monitored with blocktemperature sensors 350 installed near each heating plate 355. Inaddition, a plurality of thermistors 340 detects temperature of materialin reservoirs surrounding printing head slots 25.

According to some embodiments of the present invention, each slot 25 issurrounded by two reservoirs formed in print block base 325. Thereservoirs are shown and described in more details in reference to FIGS.5A and 5B. Optionally, eight thermistors 340 are included to monitortemperature in eight reservoirs surrounding four slots 25. Typically,printing block 120 is also installed with a thermal fuse 305 for safety.

Referring now to FIG. 4B, material from pre-heating assembly 138 reachesthe reservoirs in printing block 120 through dedicated channels 360formed in block cover 335. Typically material from chamber 130 flowsthrough check valve 310 in manifold 320 and channel 360 up to about halfway along printing block 120 in Y direction and then drips down througha cover nipple 370 into one of the reservoirs surrounding slot 25.Printing block cover 335 includes dedicated channels connecting eachpre-heat chamber 130 to one reservoir in printing block 120. Materialreaching the reservoirs is then fed into a defined array of nozzles of aprinting head installed in slot 25.

Reference is now made to FIGS. 5A and 5B showing exemplary perspectiveand top views of a printing block base of an AM system in accordancewith some embodiments of the present invention. Printing block base 325includes a plurality of slots 25 for receiving printing head 20 (FIG. 1), a frame 123 including a plurality of holes 29 for receiving springloaded lock screw 345 and a plurality of holes 27 for receiving screwsto secure printing head 20 in slot 25. According to some embodiments ofthe present invention, each slot 25 is surrounded by a pair ofreservoirs 40, e.g. reservoirs 40A and 40B, extending along a Ydirection. Typically, each reservoir 40A and 40B extend below frame 123.According to some embodiments of the present invention, a baffle orbarrier wall 30 separates reservoir 40A and from reservoir 40B.

According to some embodiments of the present invention, a height ofbarrier wall 30 is relatively low so that each of reservoirs 40A and 40Bcan be filled with different material when the fluid level is defined tobe lower than wall 30 or with a same material or a mix of material whenthe fluid level in reservoirs 40A and 40B is defined to be higher thanwall 30. Optionally, thermistors 340 (FIG. 4B) are operated to monitorand control level in each of reservoirs 40. Optionally, one or morelevel sensors are installed in reservoirs 40 to monitor and control thelevel of material contained in the reservoirs. Optionally, reservoirs 40containing support material are typically flooded so that the associatedprinting head is fully dedicated to printing support material. When onlyone material is used for a printing head 20, the material may be routedto both reservoirs 40A and 4B of a printing head 20, or only to one ofreservoirs 40 and then flooded over wall 30 to provide material in bothreservoirs 40A and 4B.

Referring now to FIG. 5B, according to some embodiments of the presentinvention, each reservoir is shaped as a defined channel with one ormore outlets, e.g. typically two outlets 45 through which material isintroduced into a printing head 20 (FIG. 1 ) installed in slot 25.Optionally, an outlet 45 is positioned on each end of reservoir 40, e.g.40A and 40B, along the Y direction. According to some embodiments of thepresent invention, reservoir 40A supplies material to a first array ofnozzles in a printing head 20 and reservoir 40B supplies material to asecond array of nozzles in the same printing head 20. Typically, thefirst and second arrays do not overlap and both arrays aresimultaneously used for printing.

In one exemplary configuration, a pre-heating assembly 138 includesresin with six different colors plus support material that is printedwith four printing heads 20.

Optionally, two out of eight pre-heat chambers 130 are fed with supportmaterial and the other six chambers are fed with different modelingmaterials, e.g. different color modeling materials. In thisconfiguration, three of printing heads 20 print with six differentcolors and one of the printing heads 20 is dedicated for printing thesupport material.

Reference is now made to FIG. 6 showing an exemplary back perspectiveview of a carriage and FIG. 7 showing an exemplary electronic pack foran AM system in accordance with some embodiments of the presentinvention. According to some embodiments of the present invention, aback of carriage 150 includes an electronic pack 400 (FIG. 7 ) partiallycovered with a casing 410. Typically, electronic pack 400 includesprinting head block board 450, printing head drivers 430 and printinghead connectors 440. Printing head connectors 440 connect each printinghead 20 to a printing head driver 430. Printing head drivers 430together with printing head block board 450 include circuitry forcontrolling printing. Typically, carriage 150 also includes a fan 420for cooling electronic pack 400.

Reference is now made to FIG. 8 showing an exemplary printing head inaccordance with embodiments of the present invention. According to someembodiments of the present invention, printing head 20 includes a nozzlesurface 22 with at least a first array of nozzles 28A and a second arrayof nozzles 28B. In some exemplary embodiments, material contained inreservoir 40A is directed to first array of nozzles 28A and materialcontained in reservoir 40B is directed to second array of nozzles 28B.In some exemplary embodiments, printing head 20 includes a singleprinting head board 21 that is connected to electronic pack 400. Using asingle printing head board 21 as opposed to a double printing head board21 improves the compactness of carriage 150. In addition the board facessideways, e.g. flat along the Y-Z plane instead of straight, e.g. flatalong the X-Z plane.

Reference is now made to FIG. 9 showing an exemplary perspective view ofa printing carriage installed with printing heads in accordance withsome embodiments of the present invention. A printing head 20 isintroduced into each of slots 25 so that nozzle surface 22 is belowprinting block 120. In one exemplary embodiment, printing block 120includes slots for four printing heads 20.

It is noted that although many of the embodiments of the presentinvention have been described in reference to a block cartridge 150 thatincludes eight pre-heat chambers 130 and four printing heads 20, thesenumbers are only exemplary and the present invention can also beimplemented with a different number of pre-heat chambers 130 and adifferent number of printing heads 20.

Reference is now made to FIG. 10 showing an exemplary top view ofanother printing block base of an AM system and to FIG. 11 showing anexemplary perspective view of the printing block base installed with twoheating plates both in accordance with some embodiments of the presentinvention. According to some exemplary embodiments, a printing blockbase 326 provides for maintaining a portion of the building materialdeposited in reservoirs 40 at a first temperature and another portion ofthe building material deposited in reservoir 41 at a second temperature.Typically, printing block base is installed with a first heating plate358 for heating building material in reservoirs 40 and a second heatingplate 356 for heating building material in reservoir 41. Typically, asecond set of first heating plate 358 and second heating plate 356 isalso installed on an opposite surface of printing block base 326. Inbetween first heating plate 358 and second heating plate 356, a cutout357 may be placed to reduce heat transfer between the plates.Optionally, printing block 326 includes one or more spaces 24 thatreduce heating transfer between reservoirs 40 and reservoir 41.Optionally, reservoir 41 is a single reservoir 41 along a side of slot26 that is proximal to an edge of printing block base 326 and distal toreservoirs 40. Typically reservoir 41 provides material for a printinghead installed in slot 26. Optionally, slot 26 may be larger in volumethan slots 25. Distancing reservoir 41 from reservoirs 40 may also helpto reduce heat transfer.

In some exemplary embodiments it is desired to maintain modelingmaterial in print block base 326 at a first temperature and to maintainsupport material at a second temperature. Typically, the supportmaterial is maintained at a lower temperature than the modelingmaterial, e.g. 2-10 degrees lower. Alternatively, it may be desirable tomaintain one type of modeling material at a different temperature thanthe others and that one type may be delivered to reservoir 41. Printblock base 326 is shown to include two thermally independent sections.Section 326A includes slots 25, reservoirs 40 and heating plates 358 andsection 326B includes slot 26, reservoir 41 and heating plates 356.Alternatively, a print block base may include more than two thermallyindependent sections or two thermally independent that are divided in adifferent manner, e.g. each section may be associated with more than oneslot. Optionally, each slot and corresponding reservoir may be thermallyindependent from the others so that different material may besimultaneously pre-heated to different temperatures.

Reference is now made to FIG. 12A showing a back perspective view of thecomponents of a printing block assembly in surface contact with apre-heater assembly for an AM system and to FIG. 12B showing a backperspective view of internal components of a pre-heating assembly for anAM system that is separated into two sections both in accordance withsome embodiments of the present invention. According to some embodimentsof the present invention, a pre-heating assembly 139 includes a firstsection 139A with a plurality of pre-heat chambers heated to a firsttemperature and a second section 139B with at least one pre-heat chamberheated to a second temperature. In some exemplary embodiments flange 137is also divided into first section 137A through which a plurality ofinlets are introduced and a second section 137B through which anotherinlet 135, e.g. inlet for support material is introduced. According tosome exemplary embodiments, each of pre-heating assembly 137A and 137Bis mounted on a manifold 320 including check valves for each of thepre-heat chamber.

Typically, each pre-heating assembly 139A and 139B includes its ownheating plate 132A and 132B and a dedicated insulator 133A and 133Brespectively. In some exemplary embodiments, block cover 335 is alsodivided into separate units. A first unit 335A covers area on block base326 for receiving material at the first temperature and second unit 335Bcovers an area on block base 326 for receiving material at the secondtemperature. Optionally, heating plate 132B extends over only a portionof pre-heat chamber while heating plate 132A may extend oversubstantially the entire length of pre-heat chambers 130A. Optionally,heating plate 132B is positioned to be proximal to printing block anddistal to inlet 135. Pre-heating assembly 139 is shown to include twothermally independent sections. Section 139A includes chambers 130A,heating plate 132A and insulator 133A and section 139B includes chambers130B, heating plate 132B and insulator 133B. Likewise other componentsof the printing block assembly are shown to include two thermallyindependent sections each including a separated block covers 335 andflanges 137. Alternatively, printing block assembly (includingpre-heating assembly 139) may include more than two thermallyindependent sections or two thermally independent sections that aredivided in a different manner, e.g. each section may be associated withmore than one material. Optionally, each chamber 130 may be thermallyindependent from the others so that each material may be pre-heated to adifferent temperature.

Reference is now made to FIG. 13 showing a front perspective view ofanother exemplary carriage and to FIG. 14 showing a perspective view ofinternal components of another pre-heater for an AM system that isseparated into two sections both in accordance with some embodiments ofthe present invention. According to some embodiments of the presentinvention, a carriage 550 includes a pre-heating assembly 538 that isseparated from and is not directly in contact with manifold 320 (whichincludes the check valves 310) located on printing block 120. Tubes maybe used to connect the channels of the pre-heating assembly 538 tomanifold 320. In some exemplary embodiments, pre-heater assembly 538includes a first section 538A with a plurality of pre-heating chambersheated to a first temperature and a second section 538B with at leastone pre-heat chamber heated to a second temperature. Typically, eachpre-heating assembly 538A and 538B includes its own heating plate 532Aand 532B respectively. Optionally, heating plate 532B extends over onlya portion of pre-heat chamber while heating plate 532A may extend oversubstantially the entire length of pre-heat chambers 130A. Optionally,heating plate 132B is positioned to be proximal to inlet 135. Asdiscussed in reference to FIGS. 12A and 12B pre-heater assembly 538 andmanifold 320 may include more than two thermally independent sections ortwo thermally independent sections that are divided in a differentmanner. Optionally, each chamber 130 may be thermally independent fromthe others so that each material may be pre-heated to a differenttemperature.

Reference is now made to FIG. 15 showing a front perspective view of yetanother exemplary carriage and to FIG. 16 showing a perspective view ofinternal components of yet another pre-heater for an AM system that isseparated into two sections both in accordance with some embodiments ofthe present invention. According to some embodiments of the presentinvention, a carriage 650 includes a pre-heating assembly 638 mounted onmanifold 320 (including the check valves 310). Pre-heating assembly 638is separated from and is not directly in contact with printing block120. Manifold 320 may be divided into a first section 320A through whichmaterial that is pre-heated to a first temperature is delivered and asecond section 320B through which material that is pre-heated to asecond temperature is delivered. Tubes may be used to connect manifold320 of preheating assembly 638 to printing block 120. In some exemplaryembodiments, pre-heating assembly 538 includes a first section 538A witha plurality of pre-heat chambers heated to a first temperature and asecond section 538B with at least one pre-heat chamber heated to asecond temperature. Typically, each pre-heating assembly 538A and 538Bincludes its own heating plate 532A and 532B respectively. Optionally,heating plate 532B extends over only a portion of pre-heat chamber whileheating plate 532A may extend over substantially the entire length ofpre-heat chambers 130A. Optionally, heating plate 132B is positioned tobe proximal to inlet 135.

According to embodiments as described for example in reference to FIGS.10-16 , a carriage may simultaneously heat a first set of materials,e.g. modeling material to a first temperature and heat a secondmaterial, e.g. support material to a second temperature so that both thefirst and second material may be simultaneously deposited each at atemperature that is suitable for that material. In some exemplaryembodiments, a same printing block base is used and the differenttemperatures are controllably achieved without significantly increasingthe footprint of the printing block base. The carriage may include morethan two thermally independent sections or two thermally independentsections each of which include more than one material passing though.Optionally, each chamber 130 may be thermally independent from theothers so that each material may be pre-heated to a differenttemperature while for example simultaneously printing with all thematerials.

Reference is now made to FIG. 17 presenting a graph showing thetemperature behavior over time in various locations of a printing blockin accordance with some embodiments of the present invention. Curves 710show exemplary temperatures measured over time at two opposite endsalong the Y axis of the walls around slots 25 and reservoirs 40 (FIG. 10). Curves 720 show exemplary temperatures measured over time at twoopposite ends along the Y axis of the walls around slot 26 and reservoir41 (FIG. 10 ). As can be seen, the temper around slot 26 and reservoir41 were maintained at a steady temperature below the temperatures aroundslots 25, as desired. In addition, the temperatures around slots 25 andreservoirs 41 were also maintained at a steady temperature, as desired.In specific embodiments of the present invention, the temperature aroundslots 25 and reservoirs 40 is maintained at about 70° C., while thetemperature around slot 26 and reservoir 41 is maintained at about 65°C.

It is the intent of the Applicant(s) that all publications, patents andpatent applications referred to in this specification are to beincorporated in their entirety by reference into the specification, asif each individual publication, patent or patent application wasspecifically and individually noted when referenced that it is to beincorporated herein by reference. In addition, citation oridentification of any reference in this application shall not beconstrued as an admission that such reference is available as prior artto the present invention. To the extent that section headings are used,they should not be construed as necessarily limiting. In addition, anypriority document(s) of this application is/are hereby incorporatedherein by reference in its/their entirety.

What is claimed is:
 1. An additive manufacturing system comprising: a printing block comprising: a plurality of slots for receiving a plurality of inkjet printing heads from which a building material is selectively dispensed for building a 3D object; a plurality of reservoirs, wherein each of the plurality of reservoirs at least partially surrounds one of said slots and is configured to feed a respective printing head installed in said slot; and at least one heating plate configured to heat building material in the plurality of reservoirs at a first temperature; and a pre-heating assembly mounted over the printing block, the pre-heating assembly comprising: a plurality of pre-heating chambers configured to supply building material to the plurality of reservoirs of the printing block; and at least one pre-heating plate configured to pre-heat building material in the plurality of pre-heating chambers.
 2. The additive manufacturing system of claim 1, wherein each of the plurality of pre-heating chambers is in fluid communication with one of the plurality of reservoirs formed in the printing block.
 3. The additive manufacturing system of claim 1, further comprising: a manifold including a plurality of valves, each of the plurality of valves being in fluid communication with one of the plurality of pre-heat chambers; and a block cover including a plurality of channels configured to connect each of the plurality of pre-heat chambers to one of the plurality of reservoirs, wherein the block cover is positioned between the printing block and the manifold.
 4. The additive manufacturing system of claim 3, wherein the block cover is divided into a first block cover section including at least one of the plurality of channels and a second block cover section, separate from the first block cover section including the other of the plurality of channels.
 5. The additive manufacturing system of claim 3, wherein the block cover includes a plurality block cover slots through which the plurality of printing heads are received in the printing block, and wherein the block cover is divided into a first block cover section including at least one of the plurality of slots and a second block cover section, separate from the first block cover section including the other of the plurality of slots.
 6. The additive manufacturing system of claim 1, wherein at least one of the plurality of pre-heating chambers includes a heat conductive worm screw configured to allow liquid building material to run downwards around said worm screw.
 7. The additive manufacturing system of claim 1, wherein the at least one heating plate on the printing block includes: a first heating plate configured to heat building material in a first portion of the plurality of reservoirs at a first temperature; and a second heating plate configured to heat building material in a second portion of the plurality of reservoirs at a second temperature, the second temperature being other than the first temperature.
 8. The additive manufacturing system of claim 7, wherein the printing block includes at least one hollowed space configured to reduce heat transfer between the first portion of the plurality of reservoirs and the second portion of the plurality of reservoirs.
 9. The additive manufacturing system of claim 7, wherein the first heating plate and the second heating plate are configured to concurrently maintain the building material in the first and second portions at different temperatures.
 10. The additive manufacturing system of claim 7, wherein the at least one heating plate includes a first additional heating plate configured to heat building material in the first portion, wherein the first heating plate and the first additional heating plate are installed on opposing surfaces of the printing block.
 11. The additive manufacturing system of claim 10, wherein the at least one heating plate includes a second additional heating plate configured to heat building material in the second portion, wherein the second heating plate and the second additional heating plate are installed on opposing surfaces of the printing block.
 12. The additive manufacturing system of claim 7, wherein the at least one pre-heating plate in the pre-heating assembly includes: a first pre-heating plate configured to pre-heat the building material in a first portion of the plurality of pre-heating chambers that supply the first portion of the plurality of reservoirs; and a second pre-heating plate configured to pre-heat the building material in a second portion of the plurality of pre-heating chambers that supply the second portion of the plurality of reservoirs.
 13. The additive manufacturing system of claim 12, wherein the pre-heating assembly includes a first insulator configured to insulate the first portion of the plurality of pre-heating chambers and a second insulator configured to insulate first second of the plurality of pre-heating chambers.
 14. The additive manufacturing system of claim 7, wherein the pre-heating assembly further includes at least one flange mounted on the plurality of pre-heating chambers, wherein the flange includes an inlet to each one of the plurality of pre-heating chambers.
 15. The additive manufacturing system of claim 14, wherein the at least one flange includes a first flange including an inlet to each one of the plurality of pre-heating chambers supplying the first portion and a second flange including an inlet to each one of the plurality of pre-heating chambers supplying the second portion.
 16. The additive manufacturing system of claim 7, wherein the building material includes a support material and a modeling material and wherein the first heating plate is configured to heat the support material and the second heating plate is configured to heat the modeling material.
 17. An additive manufacturing system comprising: a printing block comprising: a plurality of slots for receiving a plurality of inkjet printing heads from which a building material is selectively dispensed for building a 3D object; a plurality of reservoirs, wherein each of the plurality of reservoirs at least partially surrounds one of said slots and is configured to feed a respective printing head installed in said slot; a first heating plate configured to heat building material in a first portion of the plurality of reservoirs at a first temperature; and a second heating plate configured to heat building material in a second portion of the plurality of reservoirs at a second temperature, the second temperature being other than the first temperature; and a pre-heating assembly comprising: a plurality of pre-heating chambers configured to supply building material to the plurality of reservoirs of the printing block; a first pre-heating plate configured to heat building material to be supplied to the first portion; and a second pre-heating plate configured to heat the building material to be supplied to the second portion.
 18. The additive manufacturing system of claim 17, wherein the printing block includes at least one hollowed space configured to reduce heat transfer between the first portion of the plurality of reservoirs and the second portion of the plurality of reservoirs.
 19. The additive manufacturing system of claim 17, wherein the first heating plate and the second heating plate are configured to concurrently maintain building material in the first portion of the plurality of reservoirs and building material in the second portion of the plurality of reservoirs at different temperatures.
 20. The additive manufacturing system of claim 17, wherein the building material includes a support material and a modeling material and wherein the first heating plate is configured to heat the support material and the second heating plate is configured to heat the modeling material. 